The expectation of trans medical care being 100% safe and never having a negative outcome is not consistent with any other kind of medical care.
People have negative outcomes and regret in all other genres of healthcare. There is very often a risk/reward analysis that patients and doctors have to assess when considering various medications and treatments. And the risks come to fruition more than healthy people probably realize. The number of side effects I, myself, have experienced would probably shock some people. But under the circumstances, my doctor and I felt it was a risk worth taking if it would improve my quality of life.
Even elective cosmetic procedures have risks that have been accepted for decades. Breast implants often have to be redone or removed. They can have serious complications. People think it is such a benign procedure without much risk and it really is not. Yet I see no legislature trying to ban them for minors.
These lawmakers want to hold gender affirming care to an impossible standard despite a truly remarkable low regret rate.